The Democratic Unionists have sought suspension or adjournment of the Assembly until intensive cross-party talks on the paramilitarism crisis are completed and have halted meetings of the ministerial Executive.

The SDLP met the Irish premier this morning as pressure mounted on the smaller parties in the Northern Ireland Executive to adjourn the Assembly as a means to avert the suspension or collapse of powersharing over a murder linked to members of the IRA.

The Democratic Unionists have sought suspension or adjournment of the Assembly until intensive cross-party talks on the paramilitarism crisis are completed and have halted meetings of the ministerial Executive.

DUP MP Ian Paisley Jnr said the powersharing institutions were worth nothing if they were corrupted.

"The situation is about making sure the culprits who are destroying the process in Northern Ireland, namely the IRA and their fellow travellers in Sinn Fein, that they are the people who are punished. And we are doing our best to ensure that happens and if possible save the institutions," he said.

"But the institutions aren't worth anything if they are corrupted in this way. So we have got to get that balance right. It is a very, very tricky time."

Mr Paisley was speaking in Gibraltar, where he was visiting as a member of the All Party Parliamentary Group on Gibraltar.

Asked if he was willing to resign if that is what it takes, he said: "Unfortunately yes I think we have to put these things on the line."

He added: "I think it is very important that Sinn Fein now does the right thing. This is about credibility. This is about making sure that the gangsterism and the terrorism is now over once and for all."

Prime Minister David Cameron is "gravely concerned" about the situation and was phoning Mr Robinson and Northern Ireland Secretary Theresa Villiers to discuss developments, said Downing Street.

Sinn Fein's Martin McGuinness and Gerry Adams speak to the press at Stormont

Mr Cameron's official spokeswoman added: "The Prime Minister is gravely concerned about the situation. As he was saying in the House yesterday, we want to see all politicians in Northern Ireland working together to build a better future for the country and working to fulfil its great potential.

"We have been encouraging talks between the parties so they can work through their issues."

Asked whether the PM was considering suspending the Assembly, the spokeswoman said: "There are obviously now different people calling for different things, and the Prime Minister's calls with the Secretary of State and the First Minister are an opportunity for us to consider what steps should be taken next."